Investigation of noise exposure levels and assessment of hearing loss risk in a car seat manufacturing enterprise

Objective To investigate the noise exposure level and hearing loss situation of workers in a car seat manufacturing enterprise and to assess the risk of noise-induced hearing loss.

Methods A field survey was conducted in a car seat manufacturing enterprise, with 548 workers as the research subjects. Pure tone audiometry and individual noise measurement(L_{EX, 8 h}) were carried out, and the cumulative noise exposure(CNE) was calculated. The differences in hearing loss among workers with different types of job tasks, work time, and CNE were analyzed, and the potential hearing threshold changes and the risk of noise-induced hearing loss for each work position in 20-40 years of noise exposure were calculated according to the guidelines for noise occupational disease hazard risk management.

Results From September to December 2022, the median age of the 548 workers was 39 years, with a median noise exposure time of 15 years. 36.6%of the work positions had a noise 8 h equivalent sound level exceeding 85 dB(A), with an average of 86.1 dB(A), and the average CNE was 96.6 dB(A)·year. 51 cases of high-frequency hearing loss(detection rate 9.31%) and 15 cases of high-frequency combined with speech-frequency hearing loss(detection rate 2.74%) were detected, for a total hearing loss detection rate of 12.05%. The detection rate of hearing loss increased with the increase in workers' noise exposure time(P < 0.01), and the workers with work time > 15 years had the highest detection rate of hearing loss. With the increase in CNE, the proportion of hearing loss also increased gradually(P < 0.05), and the workers in the group with CNE > 100 dB(A)·year had a higher detection rate of hearing loss than workers in the other three groups. It is estimated that the risk level of hearing loss for assembly workers was medium, and the risk levels of high-frequency hearing loss and high-frequency combined with speech frequency hearing loss for welding workers were low and medium after more than 30years of noise exposure.

Conclusions The noise hazard in the car seat manufacturing enterprise is serious. Measures such as source control of noise level, establishment of an effective hearing protection program, and optimization of organizational management measures should be taken to reduce the risk of noise exposure for low-and medium-risk noise positions.Annual assessment of noise-induced risk and strengthening of hearing health monitoring for workers with noise exposure years > 30 years should be emphasized to effectively protect the hearing health of workers.